NIFI-9283 Exclude Log4j 1.2 and Upgrade Log4j2 to 2.14.1

[exceptionfactory]

Description of PR

NIFI-9283 Excludes Log4j 1.2 using Maven coordinates log4j:log4j from all referencing modules and also upgrades older versions of Log4j2 to 2.14.1.

The Encrypt Config Tool included direct usage of Log4j 1.2 and now depends on SLF4J Simple logging. Several unit tests included unnecessary references to the Log4j 1.2 BasicConfigurer.

These changes address several vulnerabilities associated with optional Socket Appenders in Log4j 1.2 and earlier versions of Log4j2.

The Maven Enforcer Plugin configuration also includes log4j:log4j as a banned dependency to avoid potential future inclusion of Log4j 1.2. As noted in comments and changes, log4j-over-slf4j should be used to provide a runtime bridge from Log4j to SLF4J.

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[gresockj]

Overall approach looks good -- I see one dependency that was missed, perhaps due to NIFI-8002 recently being merged:

$ find . -type f -name 'log4j*'
./work/nar/extensions/nifi-elasticsearch-client-service-nar-1.15.0-SNAPSHOT.nar-unpacked/NAR-INF/bundled-dependencies/log4j-core-2.14.1.jar
./work/nar/extensions/nifi-elasticsearch-client-service-nar-1.15.0-SNAPSHOT.nar-unpacked/NAR-INF/bundled-dependencies/log4j-api-2.14.1.jar
./lib/log4j-over-slf4j-1.7.32.jar

Edit: actually, on second inspection, this would be the Log4j2 update to 2.14.1 you referenced. Disregard!

[gresockj]

Thanks for this PR, @exceptionfactory. I verified that the logging still looks good in nifi-toolkit and NiFi. Will merge!